Betulinic acid attenuates lipopolysaccharide-induced vascular hyporeactivity in the rat aorta by modulating Nrf2 antioxidative function.

Betulinic acid (BA), a pentacyclic triterpenoid, has been reported to inhibit cardiovascular dysfunction under sepsis-induced oxidative stress. Nuclear factor erythroid-2 related factor-2 (Nrf2) is regarded as a key transcription factor regulating expression of endogenous antioxidative genes. To explore the preventive effects of BA against vascular hyporeactivity and the related antioxidative mechanism in sepsis, contraction and relaxation in aortas isolated from lipopolysaccharide (LPS)-challenged rats were performed. Male Sprague-Dawley rats were pretreated with brusatol (Bru, 0.4 mg/kg/2 days, i.p.), an inhibitor of Nrf2, and BA (10, 25, 50 mg/kg/day, i.g.) for 3 days and injected with LPS (10 mg/kg, i.p.) at the 4th day. Rats were anesthetized and killed by cervical dislocation after they were treated with LPS for 4 h. Thoracic aortas were immediately dissected out to determine contraction and relaxation using the organ bath system. Pro-inflammatory factors interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) and oxidative stress were measured in aortic tissues and plasma. mRNA expression of Nrf2-regulated antioxidative enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GPx), and heme oxygenase-1 (HO-1), in rat aortas was determined. Increases of IL-1ß, TNF-α, nitric oxide, and malondialdehyde and the decrease of glutathione induced by LPS were significantly attenuated by pretreatment with different doses of BA in plasma and aortas (p < 0.05 versus LPS), all of which were blocked by Bru (p < 0.01). Inhibition of phenylephrine (PE)- and KCl-induced contractions and acetylcholine (ACh)-induced vasodilatation in aortas from LPS-challenged rats was dose-dependently reduced by BA (p < 0.05; percentage improvements by BA in PE-induced contraction were 55.38%, 96.41%, and 104.33%; those in KCl-induced contraction were 15.11%, 23.96%, and 22.96%; and those in ACh-induced vasodilatation were 16.08%, 42.99%, and 47.97%), all of which were reversed by Bru (p < 0.01). Improvements of SOD, GPx, and HO-1 mRNA expression conferred by BA in LPS-challenged rat aortas were inhibited by Bru (p < 0.01; 145.45% versus 17.42%, 160.69% versus 22.76%, and 166.88% versus 23.57%). These findings suggest that BA attenuates impairments of aortic contraction and relaxation in LPS-challenged rats by activating Nrf2-regulated antioxidative pathways.

Inhibition of HDAC3 prevents diabetic cardiomyopathy in OVE26 mice via epigenetic regulation of DUSP5-ERK1/2 pathway.

Inhibition of total histone deacetylases (HDACs) was phenomenally associated with the prevention of diabetic cardiomyopathy (DCM). However, which specific HDAC plays the key role in DCM remains unclear. The present study was designed to determine whether DCM can be prevented by specific inhibition of HDAC3 and to elucidate the mechanisms by which inhibition of HDAC3 prevents DCM. Type 1 diabetes OVE26 and age-matched wild-type (WT) mice were given the selective HDAC3 inhibitor RGFP966 or vehicle for 3 months. These mice were then killed immediately or 3 months later for cardiac function and pathological examination. HDAC3 activity was significantly increased in the heart of diabetic mice. Administration of RGFP966 significantly prevented DCM, as evidenced by improved diabetes-induced cardiac dysfunction, hypertrophy, and fibrosis, along with diminished cardiac oxidative stress, inflammation, and insulin resistance, not only in the mice killed immediately or 3 months later following the 3-month treatment. Furthermore, phosphorylated extracellular signal-regulated kinases (ERK) 1/2, a well-known initiator of cardiac hypertrophy, was significantly increased, while dual specificity phosphatase 5 (DUSP5), an ERK1/2 nuclear phosphatase, was substantially decreased in diabetic hearts. Both of these changes were prevented by RGFP966. Chromatin immunoprecipitation (ChIP) assay showed that HDAC3 inhibition elevated histone H3 acetylation on the DUSP5 gene promoter at both two time points. These findings suggest that diabetes-activated HDAC3 inhibits DUSP5 expression through deacetylating histone H3 on the primer region of DUSP5 gene, leading to the derepression of ERK1/2 and the initiation of DCM. The present study indicates the potential application of HDAC3 inhibitor for the prevention of DCM.

Cardioprotective effects of luteolin on ischemia/reperfusion injury in diabetic rats are modulated by eNOS and the mitochondrial permeability transition pathway.

Myocardial ischemia/reperfusion (I/R) injury in diabetes is associated with oxidative stress, endothelial nitric oxide synthase (eNOS) dysfunction, and mitochondrial collapse, whereas luteolin is known to protect the cardiovascular system against diabetes and I/R injury. Here, we investigated whether luteolin pretreatment diminishes myocardial I/R injury in diabetic rats by affecting eNOS and the mitochondrial permeability transition pore (mPTP). After diabetic rats were produced by streptozotocin treatment (65 mg/kg) for 3 weeks, luteolin (100 mg·kg·d) or L-NAME (25 mg·kg·d) was administered intragastrically for 2 weeks. Hearts were then isolated and subjected to 30 minutes of global ischemia followed by 120 minutes of reperfusion. Pretreatment with luteolin significantly improved left ventricular function and coronary flow throughout reperfusion, increased cardiac tissue viability and manganese superoxide dismutase (MnSOD) activity, and reduced coronary lactate dehydrogenase release, and the myocardial malonaldehyde level in diabetic I/R rat hearts. All these improving effects of luteolin were significantly attenuated by L-NAME. Luteolin also significantly upregulated eNOS expression in diabetic rat hearts after I/R. Ca-induced mPTP opening and mitochondrial inner membrane potential reduction were significantly inhibited in ventricular myocytes isolated from luteolin-treated diabetic rats, and this effect was attenuated by L-NAME. These findings indicate that luteolin protects the diabetic heart against I/R injury by upregulating the myocardial eNOS pathway, and downstream effects include the enhancement of MnSOD and inhibition of mPTP.

The protection of luteolin against diabetic cardiomyopathy in rats is related to reversing JNK-suppressed autophagy.

Increasing evidence has shown that impaired autophagy dramatically causes myocardial hypertrophy and fibrosis in the diabetic heart, ultimately leading to diabetic cardiomyopathy (DCM). Luteolin has been reported to effectively attenuate diabetic cardiovascular injury by inhibiting oxidative stress and alleviate sepsis-induced myocardial injury by enhancing autophagy. However, whether luteolin can reduce DCM through activating autophagy and the underlying mechanism remain unclear. Here, reversing the c-Jun N-terminal kinase (JNK)-suppressed autophagy pathway by which luteolin attenuates DCM was explored. Male Sprague-Dawley rats were injected with streptozotocin to induce diabetes. After 6 weeks of diabetes, rats were treated with luteolin (50, 100 and 200 mg kg-1, i.g.) for 4 weeks. Histological and functional alterations in the diabetic heart were determined using HE staining, Masson staining and echocardiography. The expressions of myocardial miR-221, JNK, and c-Jun and autophagic vesicles in diabetes were evaluated by quantitative PCR, Western blotting and electron microscopy. Luteolin significantly improved cardiac function and attenuated myocardial disorganization and fibrosis in the diabetic rat accompanying the dose-dependent down-regulation of JNK, c-Jun, miR-221 and p62, increase of LC3-II/I and autophagic vesicles, and decrease of mitochondrial swelling in the diabetic heart. These data suggest that the protection of luteolin against DCM, at least, is related to suppressing JNK/c-Jun-regulated miR-221 and the subsequent blockage of autophagy.

Autophagy and its therapeutic potential in diabetic nephropathy.

Diabetic nephropathy (DN), the leading cause of end-stage renal disease, is the most significant microvascular complication of diabetes and poses a severe public health concern due to a lack of effective clinical treatments. Autophagy is a lysosomal process that degrades damaged proteins and organelles to preserve cellular homeostasis. Emerging studies have shown that disorder in autophagy results in the accumulation of damaged proteins and organelles in diabetic renal cells and promotes the development of DN. Autophagy is regulated by nutrient-sensing pathways including AMPK, mTOR, and Sirt1, and several intracellular stress signaling pathways such as oxidative stress and endoplasmic reticulum stress. An abnormal nutritional status and excess cellular stresses caused by diabetes-related metabolic disorders disturb the autophagic flux, leading to cellular dysfunction and DN. Here, we summarized the role of autophagy in DN focusing on signaling pathways to modulate autophagy and therapeutic interferences of autophagy in DN.

Profile of crosstalk between glucose and lipid metabolic disturbance and diabetic cardiomyopathy: Inflammation and oxidative stress.

In recent years, the risk, such as hypertension, obesity and diabetes mellitus, of cardiovascular diseases has been increasing explosively with the development of living conditions and the expansion of social psychological pressure. The disturbance of glucose and lipid metabolism contributes to both collapse of myocardial structure and cardiac dysfunction, which ultimately leads to diabetic cardiomyopathy. The pathogenesis of diabetic cardiomyopathy is multifactorial, including inflammatory cascade activation, oxidative/nitrative stress, and the following impaired Ca2+ handling induced by insulin resistance/hyperinsulinemia, hyperglycemia, hyperlipidemia in diabetes. Some key alterations of cellular signaling network, such as translocation of CD36 to sarcolemma, activation of NLRP3 inflammasome, up-regulation of AGE/RAGE system, and disequilibrium of micro-RNA, mediate diabetic oxidative stress/inflammation related myocardial remodeling and ventricular dysfunction in the context of glucose and lipid metabolic disturbance. Here, we summarized the detailed oxidative stress/inflammation network by which the abnormality of glucose and lipid metabolism facilitates diabetic cardiomyopathy.

Sestrin2 is involved in the Nrf2-regulated antioxidative signaling pathway in luteolin-induced prevention of the diabetic rat heart from ischemia/reperfusion injury.

Luteolin attenuates myocardial ischemia/reperfusion (I/R) injury in diabetes through activating the nuclear factor erythroid 2-related factor 2 (Nrf2)-related antioxidative response. Though sestrin2, a highly conserved stress-inducible protein, is regarded as a modulator of Nrf2 and reduces I/R injury, the effect of sestrin2 on luteolin-induced prevention of the diabetic heart from I/R injury remains unclear. We hypothesized that luteolin could relieve myocardial I/R injury in diabetes by activating the sestrin2-modulated Nrf2 antioxidative response. Diabetes was induced in rats using a single dose of streptozotocin (65 mg kg-1, i.p.) for 6 weeks, and then luteolin (100 mg kg-1 d-1, i.g.), Nrf2 inhibitor brusatol, or sestrin2 blocker leucine was administered for 2 consecutive weeks. After that, the hearts were isolated and exposed to global I/R (30 min/120 min). Luteolin markedly improved cardiac function, myocardial viability and expressions of Nrf2-regulated antioxidative genes, and reduced lactate dehydrogenase release, malondialdehyde, and 8-hydroxydeoxyguanosine in the diabetic I/R hearts. Ca2+-induced mitochondrial permeability transition and membrane potential disruption were markedly inhibited in luteolin-treated diabetic ventricular myocytes. All these effects of luteolin were significantly reversed by Nrf2 inhibitor brusatol or sestrin2 inhibitor leucine. Luteolin-induced diminished Keap1 and augmented nuclear translocation and ARE binding activity of Nrf2 were hampered by leucine in the diabetic I/R heart. In addition, luteolin-induced augmented transcription of sestrin2 was markedly blocked by brusatol in the diabetic I/R heart. These data suggest that sestrin2 and Nrf2 positively interact to promote antioxidative actions and attenuate mitochondrial damage, by which luteolin relieves diabetic myocardial I/R injury.

Luteolin reduces high glucose-mediated impairment of endothelium-dependent relaxation in rat aorta by reducing oxidative stress.

While luteolin, a flavone rich in many plants, has some cardiovascular activity, it is not clear whether luteolin has beneficial effects on the vascular endothelial impairment in hyperglycemia/high glucose. Here, we reveal the protective effect of luteolin on endothelium-dependent relaxation in isolated rat aortic rings exposed to high glucose. The thoracic aorta of male Sprague-Dawley rats was rapidly dissected out and the effect of luteolin on the tension of aortic rings pretreated with high glucose (44mM) for 4h was measured in an organ bath system. The levels of nitric oxide (NO), hydroxy radical (OH(-)) and reactive oxygen species (ROS), and the activity of superoxide dismutase (SOD) and nitric oxide synthase (NOS) were measured in aortas. The vasorelaxation after treatment with luteolin for 8 weeks in aortic rings from diabetic rats was also determined. We found that exposure to high glucose decreased acetylcholine-induced endothelium-dependent relaxation. However, high mannitol had no effect on vasorelaxation. Luteolin evoked a concentration-dependent relaxation in aortic rings previously contracted by phenylephrine, and the pD(2) value was 5.24+/-0.04. The EC(50) of luteolin markedly attenuated the inhibition of relaxation induced by high glucose, which was significantly weakened by pretreatment with l-NAME (0.1mM), but not by indomethacin (0.01mM). Luteolin significantly inhibited the increase of ROS level and OH(-) formation, and the decrease of NO level, NOS and SOD activity caused by high glucose. The improving effect of luteolin on endothelium-dependent vasorelaxation in diabetic rat aortic rings was reversed by pretreatment with l-NAME or methylene blue. The results indicate that the decrease of endothelium-dependent relaxation in rat aortic rings exposed to high glucose is markedly attenuated by luteolin, which may be mediated by reducing oxidative stress and enhancing activity in the NOS-NO pathway.

[Electrophysiological effect of atorvastatin on isolated rat hearts injured by ischemia/reperfusion].

OBJECTIVE: To investigate the myocardial electrophysiological effect and its underlying mechanisms of atorvastatin (Ator) on isolated rat hearts injured by ischemia/reperfusion (I/R). METHODS: Isolated SD rat hearts were mounted on Langendorff system, and a local I/R was induced by ligation (30 min) and release (15 min) of the left anterior descending artery. During the reperfusion period, the effect of Ator on diastolic excitation threshold (DET), effective refractory period (ERP) and ventricular fibrillation threshold (VFT) on rat heart were measured. RESULT: Compared with the control group, medium concentration of Ator prolonged the ERP in normal rat hearts; low, medium and high concentration of Ator significantly inhibited the decrease of DET, ERP and VFT induced by I/R. However, pretreatment with L-NAME cancelled these cardiac electrophysiological effects of Ator. CONCLUSION: Ator reduced electrophysiological alteration induced by I/R in isolated rat hearts, which may be mediated by activating nitric oxide pathway to enhance the myocardial electrophysiological stability.

Luteolin Attenuates Cardiac Ischemia/Reperfusion Injury in Diabetic Rats by Modulating Nrf2 Antioxidative Function.

Luteolin has been reported to attenuate ischemia/reperfusion (I/R) injury in the diabetic heart through endothelial nitric oxide synthase- (eNOS-) related antioxidative response. Though the nuclear factor erythroid 2-related factor 2 (Nrf2) is regarded as a key endogenous factor to reduce diabetic oxidative stress, whether luteolin reduces cardiac I/R injury in the diabetic heart via enhancing Nrf2 function needs to be clarified. We hypothesized that pretreatment with luteolin could alleviate cardiac I/R injury in the diabetic heart by affecting the eNOS/Nrf2 signaling pathway. The diabetic rat was produced by a single injection of streptozotocin (65 mg/kg, i.p.) for 6 weeks, and then, luteolin (100 mg/kg/day, i.g.), eNOS inhibitor L-NAME, or Nrf2 inhibitor brusatol was administered for the succedent 2 weeks. After that, the isolated rat heart was exposed to 30 min of global ischemia and 120 min of reperfusion to establish I/R injury. Luteolin markedly ameliorated cardiac function and myocardial viability; upregulated expressions of heme oxygenase-1, superoxide dismutase, glutathione peroxidase, and catalase; and reduced myocardial lactate dehydrogenase release, malondialdehyde, and 8-hydroxydeoxyguanosine in the diabetic I/R heart. All these ameliorating effects of luteolin were significantly reversed by L-NAME or brusatol. Luteolin also markedly reduced S-nitrosylation of Kelch-like ECH-associated protein 1 (Keap1) and upregulated Nrf2 and its transcriptional activity. This effect of luteolin on Keap1/Nrf2 signaling was attenuated by L-NAME. These data reveal that luteolin protects the diabetic heart against I/R injury by enhancing eNOS-mediated S-nitrosylation of Keap1, with subsequent upregulation of Nrf2 and the Nrf2-related antioxidative signaling pathway.

Alcohol induces relaxation of rat thoracic aorta and mesenteric arterial bed.

AIMS: The aim of this study was to investigate the effect of alcohol on rat artery and its underlying mechanism. METHODS: The tension of isolated Sprague-Dawley rat thoracic aortic rings and the pressure of rat mesenteric arterial beds perfused with different concentrations of alcohol (0.1-7.0 per thousand) were measured. RESULTS: At resting tensions, alcohol caused a concentration-dependent relaxation on endothelium-denuded aortic rings precontracted with KCl (6 x 10(-2) mol/L) or phenylephrine (PE, 10(-6) mol/L), and this effect was most evident on rings at a resting tension of 3 g. Alcohol induced much less vasodilation on endothelium-intact rings. Alcohol inhibited the CaCl(2)-induced contraction of endothelium-denuded aortic rings precontracted with KCl or PE. Incubation of rings with dantrolene (5 x 10(-5) mol/L), a ryanodine receptor blocker, or 2-aminoethyl diphenylborinate (7.5 x 10(-5) mol/L), an IP(3) receptor blocker, attenuated the vasodilating effect of alcohol on rings precontracted with PE. Alcohol also concentration-dependently relaxed rat mesenteric arterial beds precontracted with KCl (6 x 10(-2) mol/L) or PE (10(-5) mol/L), which was more potent on endothelium-denuded than on endothelium-intact beds. CONCLUSIONS: Alcohol has a vasodilating effect on rat artery depending on the resting tension. Both extracellular and intracellular Ca(2+) mobilization of vascular smooth muscle cells are involved in the vascular effect of alcohol.

Luteolin alleviates cardiac ischemia/reperfusion injury in the hypercholesterolemic rat via activating Akt/Nrf2 signaling.

Myocardial ischemia/reperfusion (I/R) injury in hypercholesterolemia is associated with oxidative stress, while luteolin is known to reduce oxidative stress by activating Akt/nuclear factor erythroid-2-related factor 2 (Nrf2) signaling and alleviate cardiac I/R injury. Here, we investigated whether luteolin pretreatment diminishes myocardial I/R injury in hypercholesterolemic rats by activating Akt/Nrf2 signaling. Hypercholesterolemic rats were produced by 2% cholesterol diet for 8 weeks. Luteolin (100 mg/kg/day, i.g.) or LY294002 was administered for the last 2 weeks. The hearts were then isolated and subjected to 30 min of global ischemia followed by 120 min of reperfusion. Pretreatment with luteolin significantly improved left ventricular function throughout reperfusion, increased cardiac tissue viability, reduced coronary lactate dehydrogenase release and the myocardial malondialdehyde level, upregulated p-Akt and p-GSK3ß expressions, inhibited nuclear translocation of Fyn, and activated Nrf2 function in hypercholesterolemic I/R rat hearts. All these improving effects of luteolin were significantly attenuated by LY294002. Ca2+-induced mitochondrial permeability transition pore (mPTP) opening and mitochondrial inner membrane potential reduction were significantly inhibited in ventricular myocytes isolated from luteolin-treated hypercholesterolemic rats, which were attenuated by LY294002. These results indicate that luteolin protects the hypercholesterolemic heart against I/R injury due to upregulation of Akt-mediated Nrf2 antioxidative function and inhibition of mPTP.

Carvedilol ameliorates endothelial dysfunction in streptozotocin-induced diabetic rats.

The beta-blocker, carvedilol has an additional endothelium-dependent vasodilating properties in patients with hypertension or heart failure. Whether carvedilol can improve endothelium-dependent relaxation in a diabetic animal model and its mechanism of action are unknown. The aim of this study was to investigate the effect of carvedilol on the endothelial-response of aortas from diabetic rats and the underlying mechanism. Acetylcholine-induced endothelium-dependent relaxation, sodium nitroprusside (SNP)-induced endothelium-independent relaxation, and expression of nitric oxide synthase 3 (NOS3) mRNA were measured in aortas isolated from both non-diabetic and streptozotocin-induced diabetic rats. The level of NO in serum was also measured 5 weeks after carvedilol administration (1 or 10 mg/kg/day). Endothelium-dependent relaxation declined along with the decrease of serum NO level in aortas from diabetic rats. Treatment with carvedilol for 5 weeks prevented the inhibition of endothelium-dependent relaxation and the decrease of serum NO levels caused by diabetes. The expression of NOS3 mRNA, protein expression and NOS3 phosphorylation at Ser1177 in diabetic rat aorta was very low in untreated diabetic aortas compared with the healthy group. Administration of carvedilol not only significantly increased the expression of NOS3 mRNA but also protein expression and NOS3 phosphorylation at Ser1177 in the healthy and diabetic groups. In conclusion, chronic carvedilol administration significantly ameliorated the endothelial dysfunction in diabetic rat aortas, in which increased NO level, up-regulated NOS3 mRNA and phosphorylation at Ser1177 may be involved.

Carvedilol improved diabetic rat cardiac function depending on antioxidant ability.

The risk for cardiovascular disease is significantly high in diabetes mellitus. Oxidative stress plays a dominant role in the pathogenesis of diabetes mellitus. Bcl-2 gene has a close connection with antagonizing oxidative stress destroy in many diseases including diabetes. Carvedilol, an adrenoceptor blocker, also has antioxidant and free radical scavenger properties. To study the effect of carvedilol on the antioxidant status and expression of Bcl-2 in healthy and diabetic hearts, we investigated carvedilol-administrated healthy and streptozotocin-induced diabetic rats. After small and large dosage (1 or 10mg/kg/d) carvedilol-administrated for 5 weeks, hemodynamic parameters, the levels of malondialdehyde (MDA), the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and expression of Bcl-2 mRNA in the cardiac tissues of all six groups were measured. Diabetic rats had higher left ventricular end diastolic pressure (LVEDP), lower maximal rate of rise/fall left ventricle pressure development and decline (+/-dP/dtmax). These parameters were improved by administration of carvedilol. Diabetic rats showed elevated MDA level and CAT activity, but lower activities of SOD and GSH-Px. Carvedilol treatment increased activities of antioxidant enzymes and expression of Bcl-2 in healthy rats as well as diabetic rats. These results indicate that carvedilol improves cardiac function via its antioxidant property in diabetic rats partly.

[Vascular effect of extract from mulberry leaves and underlying mechanism].

OBJECTIVE: To investigate the vascular activity of extract from mulberry leaves (EML) on rat thoracic aorta and the underlying mechanism. METHODS: Isolated thoracic rings of Sprague-Dawley rats were mounted on the organ bath and the tension of the vessel was recorded. RESULT: (1) EML produced a concentration-dependent vasorelaxation of aorta preconstricted by high K(+) (60 mmol/L) or 10(-6) mol/L phenylephrine (PE) in endothelium-intact and endothelium-denuded arteries. (2) EML at EC(50) concentration reduced the calcium dose-response curve. (3) After incubation of aorta with verapamil, EML induced vasocontraction of aorta preconstricted by PE, which was abolished by ruthenium red. CONCLUSION: The vascular effect of EML is biphasic, the vasorelaxation is greater than the vasocontraction. The vasorelaxation induced by EML may be mediated by inhibition of voltage-and receptor-dependent calcium channels in vascular smooth muscle cells, while the vasocontraction is via activation of ryanodine receptor in endoplasmic reticulum.

Exacerbation of diabetic cardiac hypertrophy in OVE26 mice by angiotensin II is associated with JNK/c-Jun/miR-221-mediated autophagy inhibition.

Both diabetes and angiotensin II (Ang II) excess trigger cardiac remodeling and dysfunction, and diabetic cardiomyopathy. We hypothesized that cardiac hypertrophy associated with the development of diabetic cardiomyopathy is worsened by increased Ang II. Male type 1 diabetic OVE26 and wild-type mice were given Ang II (sc., 1.15 mg/kg, twice a day) for 14 days. Diabetes-induced cardiac dysfunction and hypertrophy was exacerbated by Ang II treatment as determined by echocardiography, wheat germ agglutinin staining and atrial natriuretic peptide. Ang II treatment dramatically exacerbated diabetes-caused decreased LC3-II, a marker of autophagy, and increased p62, an indicator of cytosolic protein clearance. Ang II treatment also augmented diabetes-associated increased phosphorylated levels of c-Jun, JNK, mTOR, and miR-221, and decreased of p27 expression, a direct target of miR-221. Chromatin immunoprecipitation assay showed that Ang II elevated c-Jun binding to the promoter of miR-221 in diabetic mice. These results suggest that Ang II accelerates cardiac hypertrophy in the early stage of murine diabetes, probably through activation of the JKN/c-Jun/miR-221 axis and inhibition of downstream autophagy. Therefore, inhibition of Ang II or miR-221 in diabetic individuals may be a potential approach for delaying the onset and/or reducing the severity of diabetic cardiomyopathy.

Interleukin-2 protects against endothelial dysfunction induced by high glucose levels in rats.

AIMS: Interleukin-2 (IL-2) can modulate cardiovascular functions, but the effect of IL-2 on vascular endothelial function in diabetes is not known. We hypothesized that IL-2 may attenuate endothelial dysfunction induced by high glucose or diabetes. So the aim of this study was to investigate the effect of IL-2 on endothelium-response of aortas incubated with high glucose or from diabetic rats and its underlying mechanism. METHODS: Acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR), sodium nitroprusside (SNP)-induced endothelium-independent relaxation (EIR), superoxide dismutase (SOD) and nitric oxide synthase (NOS) were measured in aortas isolated from non-diabetic rats and exposed to a high glucose concentration and from streptozotocin-induced diabetic rats. RESULTS: Incubation of aortic rings with high glucose (44 mM) for 4 h resulted in a significant inhibition of EDR, but had no effects on EIR. Co-incubation with IL-2 for 40 min prevented the inhibition of EDR caused by high glucose in a concentration-dependent manner. Similarly, high glucose decreased SOD and NOS activity in aortic tissue. IL-2 (1000 U/ml) significantly attenuated the decrease of SOD and NOS activity caused by high glucose. In addition, EDR declined along with the decrease of serum NO level in aortas from STZ-induced diabetic rats. Injection of IL-2 (5000 and 50,000 U kg(-1) d(-1), s.c.) for 5 weeks prevented the inhibition of EDR and the decrease of serum NO levels caused by diabetes. CONCLUSIONS: IL-2 significantly ameliorated the endothelial dysfunction induced by hyperglycemia, in which the activation of the NO pathway and SOD may be involved.

Carvedilol protected diabetic rat hearts via reducing oxidative stress.

Oxidative stress plays a dominant role in the pathogenesis of diabetes mellitus. Bcl-2 gene has close connection with antioxidant stress destruction in many diseases including diabetes. Carvedilol, an adrenoceptor blocker, also has antioxidant properties. To study the effect of carvedilol on the antioxidant status in diabetic hearts, we investigated carvedilol-administrated healthy and streptozotocin-induced diabetic rats. After small and large dosage carvedilol-administered for 5 weeks, hemodynamic parameters, the levels of malondialdehyde, activities of antioxidant enzymes and expression of Bcl-2 mRNA in the cardiac tissues were measured. The diabetic rats not only had cardiac disfunction, weaker activities of antioxidant enzymes, but also showed lower expression of Bcl-2. Carvedilol treatment increased activities of antioxidant enzymes and expression of Bcl-2 in healthy rats as well as diabetic rats. These results indicated that carvedilol partly improves cardiac function via its antioxidant properties in diabetic rats.

[Effect of emodin on NO-cGMP signal pathway in rat vascular endothelium in vitro].

OBJECTIVE: To investigate the vasorelaxation effect of emodin and its relationship with NO-cGMP signal pathway. METHODS: Changes of tension of rat thoracic aortic rings were measured by MedLab biologic signal collection system, and the activity of total nitric oxide synthase (tNOS), constitutive NOS (cNOS) and inducible NOS (iNOS) in endothelium after being treated with emodin was determined with nitric acid reductase method. RESULTS: Emodin relaxed the phenylephrine and potasium chlorate induced contraction of aortic rings, either with or without intact endothelium, in a concentration-dependent manner. Pretreatment of no-specific potassium channel blocker strontium chloride (CsCL) could attenuate the vasorelaxation effect of emodin on aortic rings without intact endothelium, but it could not inhibit vasorelaxation of emodin on aortic rings with intact endothelium. This vasorelaxation action of emodin (40 micromol/L) could be partial blocked by NOS inhibitor L-NAME and guanylate cyclase inhibitor ODQ, with the vasorelaxation range dropped to 64.76 +/- 13.73% and 6.28 +/- 4.79% respectively. Moreover, emodin (40 micromol/L) increased iNOS activity significantly. CONCLUSION: The concentration-dependent vasorelaxation effect of emodin might act by activating the NO-cGMP pathway in vascular endothelium.